1. Field of the Invention
The present invention relates to a sewing machine, and more particularly relates to a threading device provided in connection with the sewing machine and including a threading member having a hook and vertically moved by a drive motor along a needle bar of the sewing machine. The threading member is moved down to a threading position and is then rotated to insert the hook through the needle eye of the needle which is attached to the lower end of the needle bar, wherein a series of threading operations may be smoothly and accurately.
2. Prior Art
Recently many sewing machines have come to be provided with a threading device. Various types of threading devices have been developed, and many of which include a threading member which is moved down near the needle eye of the needle and is then a hook is inserted through the needle eye. The series of threading operations are performed manually by manipulation of a lever.
Therefore, according to the prior art, it is required that the manually operated lever is held by hand until the thread is passed through the needle eye. In this case, the timing to release the lever or the force applied to the lever is inappropriate, the thread fails to pass through the needle eye. Further, the hook is often knocked against the needle instead of being inserted into the needle eye, and both may be damaged.
It is, therefore, a primary object of the invention to provide a threading device for a sewing machine which is compact in structure and smooth in operation.
It is another object of the invention to provide a threading device which is operated automatically by a drive motor such that a thread may be rapidly and accurately passed through the needle eye of needle irrespectively of the experience of the machine operator.
It is another object of the invention to provide a drive motor which may be controlled to pull a threading hook out of the needle eye at a higher speed than the speed at the time of inserting the threading hook through so that the thread hung to the inserted hook may not be slipped out.
It is another object of the invention to provide a drive motor which may be controlled to maintain the threading hook as it is inserted through the needle eye until a return signal is given.
It is another object of the invention to provide a drive motor which may be stopped to stop the operation of the threading device in case a trouble including an excessive load is detected during threading operation.
It is another object of the invention to provide a means for indicating a warm in case a trouble is produced.
It is another object of the invention to provide a cutter for cutting the thread passed through the needle eye with a predetermined length of thread remained that is sufficient enough to form the subsequent stitch without being pulled out of the needle eye.
The other objects and advantages of the invention will be apparent in the detailed description of the invention.
For attaining the objects, the invention substantially comprises a needle bar having a needle attached to the lower end thereof, the needle having a needle eye, a threading shaft having a threading member mounted to the lower end thereof, the threading member having a threading hook, a drive motor for vertically moving the threading shaft along the needle bar, guide means for guiding and rotating the threading shaft at a threading position as the same is vertically moved, a regulating member for deciding the threading position of the threading shaft, wherein the threading shaft is moved down and stopped at the threading position and is axially rotated to pass the threading hook through the needle eye and is maintained in this state until a return signal is given such that the drive motor may be driven again to pull the threading hook out of the needle eye and move up the threading shaft.